The conventional filling machine for filling beverage cans includes approximately one hundred valve assemblies which are mounted on a rotatable carrier or turret, and each valve assembly is positioned above a lift cylinder and platform which supports a can or other container to be filled with liquid. Each valve assembly is connected to a central filler tank by three tubes; a large diameter tube provides a passage for the beer or other liquid to move from the tank to the valve assembly, while two smaller diameter tubes serve to conduct carbon dioxide and air between the tank and valve assembly.
The valve assembly, as used in the conventional filling machine, includes a valve body, a rotatable disc which is mounted for rotation with respect to the valve body, and an adapter which is connected to the valve body and seals against the top of the can to be filled. Both the valve body and the disc have mating flat surfaces and ports in the disc and the valve body are adapted to be brought into registry as the disc is rotated to provide the desired liquid and gas flow between the filler tank and the can.
To rotate the disc with respect to the valve body, the conventional valve assembly includes a pair of arms which extend outwardly from the disc, and the arms are adapted to contact a series of fixed cams as the carrier rotates to thereby rotate the disc and bring the ports in the disc and valve body into proper registry.
The conventional filling machine operates at high speeds, generally filling about 1500 cans per minute. At this high speed, there is considerable impact when the arms, which are located at an angle of approximately 90.degree. with respect to the direction of movement of the valve assembly, strike the cam surfaces, resulting in substantial wear on the arms and cam surfaces, and in some cases breakage of the arms, which produces a serious maintenance problem.
As an additional problem, at high operating speeds, the arms may tend to over-ride when leaving the cam surface, that is, continue to rotate beyond the proper point of index, with the result that the ports in the disc and the valve body are not in proper registry. By increasing the biasing force between the contiguous faces of the valve body and the disc, the tendency to override can be reduced. However, increasing the biasing force will necessitate an increased force to move the arms and rotate disc, and this results in additional wear on the arms and cam surfaces. On the other hand, if the biasing force is decreased, the tendency to over-ride or boucce off the cam surface is increased, resulting in possible misalignment between the ports in the disc and the valve body.